Contact arrangement for vacuum switch including winding contact



Jan. 2, 1968 F. BACHOFEN 3,361,887

CONTACT ARRANGEMENT FOR VACUUM SWITCH INCLUDING WINDING CONTACT Filed April 20, 1967 United States Patent 3,361,887 CONTACT ARRANGEMENT FOR VACUUM SWITCH INCLUDING WINDING CONTACT Felix Bachoten, Oberentfelden, Aargau, Switzerland, as-

signor to Fabrik Elektrischer Apparate Sprecher & Schuh A.G., Aargan, Switzerland Filed Apr. 20, 1967, Ser. No. 632,387 Claims priority, application Switzerland, Apr. 20, 1966, 5,765/66 4 Claims. (Cl. 200-166) ABSTRACT OF THE DISCLOSURE This invention relates to vacuum switches having movable and stationary arcing contacts arranged within a hermetically sealed enclosure, the stationary contact being formed as a winding having one or several convolutions and the movable contact is arranged within the convolutions of the winding.

Background 0 the invention In electric switches having operating contacts situated in a high vacuum, it sufiices to provide relatively short break distances. In order to reduce as much as possible the consumption of contact material due to burning off, it is customary to displace the contact breaking arc by means of a magnetic field in such manner that also the bases or points of attachment of the are on the contacts are rapidly moved, so as to prevent a local overheating of the contact surfaces. Such a magnetic blowing of the arc can be effected in known manner by a specially provided magnet or by a field produced by the current to be switched itself, the required curving of the current paths being obtained by an appropriate shaping of the switch contacts.

The object of the present invention is the provision of a contact arrangement for solving the above outlined problem in a new and simple manner, and which is particulary advantageous for use with vacuum switches having relatively short interruption paths.

Summary of the invention The invention concerns a contact arrangement for vacuum switches having a fixed and a movable switching member, in which the stationary switching member is formed as an open winding having at least one convolution, the movable switching member being arranged within said winding, so that in breaking position it is situated substantially in the central axis of said winding without contacting the winding, and in closing position said movable switching member makes contact with the inner surface of said Winding at a point thereof at which the current has passed at least through one half of the circumference of said convolution.

Brief description of the drawings The drawing diagrammatically illustrates three embodiments of the invention.

FIGURE 1 represents a section through one pole of a vacuum switch with single interruption,

FIGURE 2 shows a feedthrough insulator with the stationary switching member of the switch according to FIG- URE 1 and the cooperating movable switching member, represented in the off-position,

FIGURE 3 shows the same members as FIGURE 2, but in the on-position,

FIGURE 4 shows a contact arrangement having a winding with several convolutions for double interruption,

FIGURE 5 is a modification having a stationary switch member similar to FIGURE 4, in which the different convolutions of the winding have a ameter.

Referring to FIGURE 1, a hermetically sealed, airtight casing 1 for one pole of a vacuum switch has inserted therein two feed-in insulators 2 and 2a. The insulator 2 carries a stationary contact member 3, and the other insulator 2a carries a fixed rod 3a provided with a journal pin 4 having pivoted thereon a contact knife 5. Actuation of the contact knife is effected by means of a link 6 pivotally connected with one end to the knife 5 at 6a, and with the other end to a drive rod 7 extending through the wall of the casing 1. In order to provide a vacuum-tight seal at the place where the rod 7 penetrates through the wall of the casing, bellows 8 have one end tightly secured around the opening in the casing for the passage of the rod 7, while the other end is brazed to the rod 7 and moves with the rod. The contact knife 5 carries a contact piece 9 at its free end, preferably consisting of a metal having a high welding resistance and superior extinguishing properties. In its off-position shown in FIGURE 2 the contact piece 9 is situated substantially in the central axis of the fixed contact piece 3 formed by a single open convolution. In the on-position the contact knife 5 is situated as shown in dash-and-dot lines in FIGURE 1 in which, as shown in FIGURE 3, the contact piece 9 makes contact with the inner circumference of the winding 3 at a point 10 at which the current has already passed through at least one half of the circumference of the single convolution. When the vacuum switch is disconnected under load, the contact piece 9 again moves into the central position shown in FIGURE 2, while a circuit breaking arc is formed, which is blown by the action of the magnetic field in the direction of the free end of the winding 3, while the points of attachment of the arc move along the surfaces of the two switch members 3 and 9.

In order to increase the magnetic blowing action, the winding of the switch member 3a in FIGURE 4 can have several convolutions, i.e. the winding is formed as a helical coil. The contact knife So can be provided for double interruption by being rigidly secured to a guide rod 11, so that the knife 5 remains parallel to itself during the switching operation.

The windings So can be made of material having a circular cross section; they can also have any other convenient profile; for example they can be formed of flat bars of rectangular cross section having rounded edges, as illustrated in FIGURE 5. In this embodiment the radius of the several convolutions of the coil 3b gradually increases towards the free end of the coil, i.e. they form a conical spiral. With a stationary coil of this shape the magnetic blowing not only produces a traveling of the points of attachment of the are along the winding 3b and the surface of the movable switch member 9, but also causes an elongation of the cont-act breaking arc until its extinction.

I claim:

1. A contact arrangement for vacuum switches having a fixed and a movable switching member, wherein the improvement comprises the provision of a stationary switching member formed as an open winding having at least one convolution, and a movable switching member arranged within said winding so that in the off-position of the switch the movable switching member is situated substantially in the central axis of said winding without contacting the winding, and in the on-position said movable switching member makes contact with the inner surface of the winding at a point thereof where the current has passed through at least one half of the circumference of said convolution.

2. A contact arrangement according to claim 1, in

gradually increasing di- 3 4 which said stationary switching member is formed as a References Cited z i z c iiitact arrangement accord g to cla'm 1 in UNITED STATES PATENTS i in 1 which said stationary switching member is formed as a 3O141O9 12/1961 Burger 200 144 helical coil having several convolutions, the radius of suc- 5 FOREIGN PATENTS cessive convolutions gradually increasing towards the free 795,830 5/1958 Great Britain end of the 0011. r 64 4. A contact arrangement according to claim 1, in 967'737 8/19 Great Bntam' which said movable switching member comprises tWo separate contact pieces formed on a common switching 10 ROBERT SCHAEFER Pnmary Examine"- bridge and cooperating each with a stationary Winding H O JONES Assistant Examiner included in the circuit to act as a double circuit breaker. 

